Confinement–Unconfinement Transformation of ILs in IL@MOF Composite with Multiple Adsorption Sites for Efficient Water Capture and Release

Abstract

However, these adsorbents have obvious drawbacks in balancing the adsorption capacity and desorption conditions because of too weak or too strong hydrophilicity. [21] Therefore, it is necessary to develop novel porous functional materials with efficient water capture and release performance from atmosphere.Metal-organic frameworks (MOFs) have emerged as a class of porous materials by self-assembly of inorganic metal clusters and organic linkers. They have high porosities and internal surface areas, as well as diversity in chemistry and structure. [24] As a result of these attractive features, MOFs are promising candidates to capture water. Recently, there is a growing interest to search novel MOFs to achieve high water uptakes. [22,25] For example, at the low relative humidity relating to water harvesting in the desert, Yaghi et al. demonstrated that substantial progress has been made in some materials, such as MOF-801, [26] and MOF-303. [27,28] At the high relative humidity, Zhao et al. utilized PNIPAM@MIL-101(Cr) to obtain high water adsorption (RH = 96%, 440 wt%). [16] In the range of test pressure, the high water adsorption capacity is mainly attributed to the specific surface area and pore volume of MOF. For instance, the water adsorption capacity of Cr-soc-MOF-1 is almost 200 wt% due to the specific surface area of 4590 m 2 g −1 and pore volume of 2.1 cm 3 g −1 , while further improvement of uptake is hindered by the limitation of pore volume. [29] Meanwhile, the release of adsorbed water is important from the practical point of view. [15] Considering the preferred low-grade waste heat sources or even low-cost solar resources, the ideal condition is that the desorption temperature should be lower than 323 K. [30][31][32] Unfortunately, the reported regeneration temperatures of most MOF materials are higher than expected. To address these challenges, developing solid-liquid hostguest composites (SLHGCs) may be a possible solution. It uses solid as the main material and functional liquid as the guest one. Porous solid material can provide limited space and strong capillary force for carrying functional liquid. [33] As a kind of functional liquid, ionic liquids (ILs) are rich in polar groups and adsorption sites, [34,35] and nano-confined ILs by loading ILs into porous materials can be a versatile strategy to prepare composites with a combination of their favorable characteristics. The impregnation of ILs inside the Water adsorption based on porous materials is of fundamental importance in atmospheric water harvesting and dehumidification. Herein, a [BOHmim] [Zn 2 Cl 5 ]@MIL-101(Cr) composite with multiple adsorption sites is designed to enhance the water adsorption capacity. It is interesting to observe that there is a water-responsive confinement-unconfinement transformation of ionic liquids (ILs) during the water adsorption and release process. Thus, it can simultaneously overcome the limitation of pore volume in traditional porous materials, and the problem of mass transfer in pure ILs. As a result, the ob...

Sorption‐Based Atmospheric Water Harvesting: Materials, Components, Systems, and Applications

“…In addition to the hygroscopic salts, MIL-101(Cr) composites with ionic liquid [60] and CNTs [61] are also studied. As a consequence of the water-responsive confinement-unconfinement switching effect of ionic liquids during the sorption and desorption process, the water sorption capacity reaches 4.77 g g −1 at a RH of 95%.…”

Confining Ionic Liquids in Developing Quasi‐Solid‐State Electrolytes for Lithium Metal Batteries

“…While for the other substrates, the confined/immobilized IL usually refers to the IL molecules up to 10 nm away from the surface of the host (Figure 1b and 1c), called general confinement, i. e., the confined-IL molecules are those within a thickness of � 10 nm. [47,[52][53][54][55] Both physical and chemical methods have been developed to achieve confinement/immobilization. Chemical coupling is one of the chemical methods, referring to the covalent grafting of ILs on the surface, which is usually accomplished by forming chemical bonding between the solid matrix and the IL with unique functional groups.…”

A novel IL/MOF nanocomposite tailored for trace SO2 efficient capture based on synergistic effects

“…[23][24][25] For example, IL/MOF composites have been extensively investigated on C 2 H 2 / C 2 H 4 separation, NH 3 , CO 2 , and H 2 O in our research group, exhibiting excellent adsorption performances. [26][27][28] Herein, a novel composite material IL/MIL was designed and synthesized, as shown in Scheme 1. The introduction of IL endows the adsorbent with unique adsorption sites (-OH, -Cl, and the long alkyl chain in IL) for SO 2 .…”

“…More importantly, the introduction of IL may provide additional adsorption sites to enhance gas adsorption and separation performance of adsorbent 23–25 . For example, IL/MOF composites have been extensively investigated on C 2 H 2 /C 2 H 4 separation, NH 3 , CO 2 , and H 2 O in our research group, exhibiting excellent adsorption performances 26–28 …”